In a manufacturing process of a semiconductor device, various films such as a Si3N4 (hereinafter referred to as silicon nitride or SiN) film and the like are formed on a semiconductor wafer (hereinafter referred to as a wafer) which is a substrate. This film forming process is performed by a method called ALD (Atomic Layer Deposition) in which a raw material gas and a reaction gas are alternately supplied to the wafer a plurality of times. As the film forming apparatus that performs ALD, there is known an apparatus configured so that a wafer is mounted on a rotary table provided inside a vacuum container and the wafer revolved by rotation of the rotary table repeatedly passes through a processing region formed of an atmosphere to which a raw material gas is supplied and a processing region formed of an atmosphere to which a reaction gas is supplied. In addition to the atmosphere of the raw material gas and the atmosphere of the reaction gas, a modifying gas for modifying a film is supplied onto the rotary table, whereby predetermined regions to which the reaction gas and the modifying gas are respectively supplied are formed. Furthermore, an isolation region for supplying a separation gas so as to separate these processing regions is formed.
In the above-described film forming apparatus, the raw material gas and the reaction gas are also supplied to the rotary table in addition to the wafer. Therefore, a film is also formed on the rotary table. For example, when the film forming temperature varies depending on the type of the wafer, the rotary table is used in a plurality of temperature zones. If the temperature of the rotary table is changed in the state in which the film is formed on the rotary table in this manner, for example, the surface layer portion of the film formed on the rotary table may be peeled off due to thermal shrinkage caused by the temperature change and may become particles. Therefore, in the related art, when film formation is not performed, the rotary table is replaced to remove the film adhering to the rotary table, or a cleaning gas is supplied into the vacuum container to perform a cleaning process of removing the film of the rotary table. However, it takes a long time to replace the rotary table. Thus, there is a problem that the throughput of the apparatus is lowered. In the case where the film adhering to the rotary table is removed by supplying the cleaning gas, the peeled-off film may remain as particles inside the film forming apparatus. Thereafter, when a film forming process is performed on the wafer, particles may adhere to the wafer.
In the related art, there is known a technique in which a purge gas is supplied to a portion on a rotary table in a separation region having a high temperature and the heated portion is cooled by allowing the heated portion to pass through a processing region, whereby a silicon oxide film formed on the rotary table is thermally shrunk and is made less likely to peel off. However, it takes time to change the temperature of the rotary table by blowing a high-temperature purge gas.
Furthermore, in the related art, there is known a technique in which, in a heat treatment apparatus for heating substrates arranged in a shelf inside a reaction container from a circumferential direction of the substrates and supplying a gas to the substrates, a purge gas is supplied into the reaction container to increase the pressure when heating and then cooling the interior of the reaction container. Then, by repeating the heating of the interior of the reaction container, and the cooling and pressure increasing a plurality of times, the film adhering to the interior of the reaction container is removed. However, there are demands for improvement of the throughput of the apparatus and for more reliable suppression of the particles. Thus, a demand has existed for further improvement.